809 
 WTPZ44 KNHC 031434
 TCDEP4
 
 HURRICANE ISELLE DISCUSSION NUMBER  12
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092014
 800 AM PDT SUN AUG 03 2014
 
 It hasn't been particularly steady, but Iselle continues on a
 gradual strengthening trend.  The eye has cleared out in infrared
 satellite imagery, and the overall presentation has become a little
 more symmetric.  Dvorak estimates are now T5.5/102 kt from SAB,
 T5.0/90 kt from TAFB, and near 110 kt from the UW-CIMSS ADT.
 Therefore, the maximum winds are set at 100 kt as a blend of these
 numbers, making Iselle a major hurricane.
 
 The intensity forecast has been complicated.  Iselle continues to
 push through the peak intensities shown in previous model cycles,
 so apparently the environment has been a little more favorable than
 expected.  Vertical shear has decreased since yesterday, but still
 the latest model runs do not show any additional intensification,
 presumably because the thermodynamic environment is becoming more
 marginal.  The NHC forecast maintains Iselle at 100 kt for the next
 12 hours and then only gradually weakens it through 48 hours, but
 given the hurricane's history, I can't rule out some additional
 strengthening in the short term.  Interestingly, the statistical
 models are stronger than the dynamical models during the first 48
 hours, but the scenario flip-flops on days 3 through 5 with the
 dynamical models maintaining a stronger cyclone as Iselle
 approaches the Hawaiian Islands.  For now, the NHC forecast closely
 follows the intensity consensus ICON and is unchanged from the
 previous advisory beyond 48 hours.
 
 The initial motion is 280/9 kt.  Ridging to the north of Iselle is
 expected to maintain a westward heading for the next 3 days, but
 the forward motion will decrease in about 36 hours as that ridge
 weakens.  After day 3, Iselle is forecast to turn west-
 northwestward and accelerate when a mid-level high develops halfway
 between Hawaii and California.  The track models are in good
 agreement for the entire forecast period, but as mentioned in the
 previous advisory, a slight northward adjustment was needed in the
 official forecast on days 4 and 5 to account for recent model
 trends.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  03/1500Z 15.5N 132.8W  100 KT 115 MPH
  12H  04/0000Z 15.6N 134.3W  100 KT 115 MPH
  24H  04/1200Z 15.7N 136.1W   95 KT 110 MPH
  36H  05/0000Z 15.7N 137.6W   90 KT 105 MPH
  48H  05/1200Z 15.8N 139.1W   80 KT  90 MPH
  72H  06/1200Z 16.5N 143.5W   65 KT  75 MPH
  96H  07/1200Z 18.0N 149.5W   55 KT  65 MPH
 120H  08/1200Z 20.0N 156.0W   45 KT  50 MPH
 
 $$
 Forecaster Berg